Fix formatting of branches ahead-behind on narrow windows (#12989)

Make the bar-groups width 50% with max-width of 90px

Fix #12252

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

web_src/less/_repository.less

@@ -1399,7 +1399,8 @@
         position: relative;
         float: left;
         padding-bottom: 6px;
-        width: 90px;
+        width: 50%;
+        max-width: 90px;
 
         &:last-child {
           border-left: 1px solid #b4b4b4;